From plastic concrete to elastic water, types of eco-friendly plastics are versatile and varied, allowing for a wide application of greener materials. Now we can add self-healing plastic to the list thanks to two different research centers. A team at Iowa State University is developing a bioplastic that can repair itself, while a group at the Fraunhofer Institute in Germany drew inspiration from the rubber tree to create a similar type of material. Both plastics would be able to naturally repair tiny surface cracks before they grew into larger, permanent fissures.

Photo credit: Jon Rawlinson

At Iowa State, a professor working on two different types of polymer research — one examining bioplastics, the other looking at self-healing plastics — combined the studies to develop a material that was both. In the field of biorenewable polymers, the team, lead by Associate Professor Michael Kessler, discovered that polymers made from vegetable oils were an excellent substitute for petroleum based plastics for environmental and economic reasons. In separate research, he found that polymers can easily repair themselves, which could solve the issues of micro-cracking and hidden damage — vital considerations for materials used in aerospace engineering. Now, with a grant from the National Science Foundation, Kessler’s team is the first in the world to attempt to create self-healing bioplastics.

Meanwhile, at the Fraunhofer Institute, researchers have already created self-healing elastomers that would increase the lifespan of thousands of everyday objects and decrease the amount of energy needed in vehicles and machines. The researchers found their inspiration in the hevea Brasiliensis rubber tree. Latex from the tree contains capsules of a special protein that break open when the bark of the tree is damaged. The protein in the latex then works to seal the wound. A scientist involved in the research explained the development process to Plastic News:

“We loaded microcapsules with a one-component adhesive (polyisobutylene) and put it in elastomers made of synthetic caoutchouc to stimulate a self-healing process in plastics. If pressure is put on the capsules, they break open and separate this viscous material. Then this mixes with the polymer chains of the elastomers and closes the cracks.”

Initial tests on a synthetic rubber by the Fraunhofer research team have indicated that the naturally occurring repair process can indeed be replicated. For Kessler’s team, the biggest obstacle will be bridging the chemical gap between the self-healing process and bioplastics. If successful, the sustainable material would provide unparalleled advantages, thanks to its multi-functionality and eco-friendly make-up.